64 COLLINGE : ON THE ANATOMY OF THE VITRINA IRRADIANS. 



In connection with my studies on tlie Asiatic slug-like molluscs, 

 I have had occasion to examine the internal structure of many genera 

 of Indian molluscs, and as these are as yet very imperfectly under- 

 stood, I cannot, in the present instance, do better than place on 

 record the results obtained. 



I have pleasure in expressing how greatly indebted I am to the 

 kindness of Mr. Oliver Collett, who has sent me many choice 

 examples of this species, as of many other Cingalese genera. 



RATNADVIPIA, Godw.-Aust. 



llatnadvipia, G.-A., Proc. Malac. Soc. Lond., 1899, vol. iii, p. 253; 

 Moll, of India, 1899, vol. ii, p. 95. 



Animal slug-like, with the mantle bordering the shell on all sides, 

 posterio-laterally produced into tongue-like extensions. Dorsum 

 flattened behind visceral hump, posteriorly sharply keeled. Caudal 

 mucous pore large. Foot-sole not divided into median and lateral 

 planes. Viscera does not extend into posterior portion of body, 

 which is solid. Intestinal tract rather short, exhibits four loops. 

 Generative system with well developed penis-sheath, containing 

 evertible penis ; diverticulum, epi[)hallus, and kalk-sac present. 

 Receptaculum seminis sessile. Uart-sac and large dart-gland,* no 

 calcareous dart, but short, blunt, muscular papilla. 



Shell thin, with few whorls, body whorl large. 



I see no objection to the name proposed by Lieut. -Col. Godwin- 

 Austen, excepting that it should rank as a distinct genus. The 

 incomplete description given by this author, and the still more 

 incomplete figures, give one very little idea of the form and structure 

 of the internal parts, and consequently the affinities, of this- very 

 interesting genus. I propose, therefore, to describe the anatomy in 

 some detail. 



The foot-sole varies much in different specimens ; in some it is 

 perfectly smooth, exhibiting no trace of a median groove, while in 

 others a well-defined median groove is present, with raised lateral 

 portions. 



Godwin-Austen thinks (1. c. p. 95) that this indicates that a 

 similar contraction prevails in life, and perhaps points to an arboreal 

 habit of the animal. This median groove is never present in 

 specimens of Girasia, preserved in alcohol, he further points out, a 



* Tlie term " dart-gl.Tntl " refers lo tlie large, almost solid portion, shown on plate v, fig. 2, (/. <jl. 

 willi a tr.iiisversc section on plate vi, fig. 10. 



